This statement asserts that the entirety of existence, the 'All,' is fundamentally consciousness, or Mind. The physical universe you perceive is merely a manifestation or thought-form within this greater mental ocean. It suggests that what we consider solid reality is, in essence, a mental construct, akin to a dream or an idea. The world appears as it does because the Universal Mind conceives of it in that manner.

The Hermetic tradition, particularly as presented in texts attributed to Hermes Trismegistus, emphasizes the principle of Mentalism. This principle posits that the All is Mind, and the universe is mental. This is not merely a philosophical observation but a foundational truth about the nature of existence. It implies that the laws governing the cosmos are mental laws, and that by understanding your own mind, you can begin to understand the workings of the universe. The illusion of separation between yourself and the All dissolves when you recognize that you are a thought within the Universal Mind, and the universe is the grand thought of which you are a part. The Kybalion, a modern Hermetic text, elaborates on these seven principles, with Mentalism being the first and most crucial.

In your life: Recognize that your thoughts shape your perception of reality. By consciously directing your mind, you can influence your experience and align yourself with the greater mental order.